In numerous technical and industrial applications, there is a need to use materials which are relatively friable, even if they show a degree of stiffness when presented in the form of plates or panels, optionally covered with a protective sheet glued over one of the large-dimension faces. These materials can generally withstand extraction forces only if the forces are spread widely so as to keep force density per unit area as low as possible.
However, it is clear that in some cases it is not possible to spread the applied forces in such a way, in particular when it is necessary, for example, to fix external elements on such panels using peg- or plug-type fixing systems.
The pegs currently used are unsuitable for achieving this aim. They include a spike which may optionally be twisted and which is surmounted by a head and they are not retained in friable material since the retention forces exerted on the spike by the material are insufficient to prevent the slightest force applied to the head pulling this type of peg out of the material. Naturally, there are other systems which comprise a peg that is placed in a lead hole made in the material, with the end of the peg that is inserted in the hole being capable of being expanded sufficiently to anchor itself against the side wall of the lead hole. This technique is not satisfactory either, since the very large forces exerted by said expanding end rapidly destroy the wall of the hole, thus reducing fixing reliability.
The object of the present invention is to mitigate the above-mentioned drawbacks and provide a peg for fixing in friable materials with retention forces that can be spread over a maximum amount of area in order to enable the peg to be held in the material more reliably than prior art pegs.